No sensitive and objective means of assessing the presence and state of activity of periodontal disease are presently available. Inflammation and degradation of the periodontal tissues are characteristic features of periodontal disease. The inflammatory exudate of the dento-gingival vascular plexus appears in the gingival crevice and gingival crevicular fluid (GCF). About 70% of the collagen is lost in the advancing front of a progressive periodontal lesion. It is generally accepted that degradation of collagen can be monitored by determination of released hydroxyproline (HYP). The proposed experiments are designed to test the hypothesis that active breakdown of collagen in the gingival tissues in progressive periodontal disease can be monitored by increased levels of HYP in GCF. Periodontal health will be established in systemically healthy beagle dogs. The dogs will be placed on a HYP-restrictive diet, then the effects of diet and circadian variation on plasma HYP levels determined. Specimens of healthy, gingival connective tissue will be obtained and analyzed for peptide and free HYP. The oral hygiene regime will be discontinued and HYP concentrations in GCF monitored at regular intervals during the development and progression of experimental gingivitis. When overt gingivitis has been established, gingival specimens will be collected from all sites used for sampling GCF and a biopsy from the advancing front of the periodontal lesion analyzed for peptide and free HYP. Dogs with overt gingivitis will be used for the conversion of established gingivitis into experimental, progressive periodontitis. GCF will be collected at regular intervals and analyzed for HYP. When significant loss of attachment has occurred, gingival specimens will be obtained and the advancing front of the periodonatal lesion analyzed for peptide and free HYP. The HYP titers in GCF will be analyzed for the postulated, positive correlation with peptide and free HYP titers in the gingival specimens. Plasma samples willl be collected whenever GCF or tissue is sampled to provide baseline HYP values.